1. Field of Invention
The field of the currently claimed embodiments of this invention relates to non-invasive methods and systems of producing cardiac electrogram characteristic maps for use in catheter ablation of ventricular tachycardia.
2. Discussion of Related Art
Radiofrequency catheter ablation is increasingly used as an adjunct to implantable cardioverter defibrillators (ICD) and medical therapy for management of scar-related ventricular tachycardia (VT) in patients with ischemic and nonischemic cardiomyopathy.1-9 Due to hemodynamic instability, the majority of scar-related VTs are unmappable during tachycardia. Consequently, significant progress has been made in substrate-guided VT ablation based on electrogram (EGM) characteristics as surrogates of the scar substrate on electroanatomic maps (EAMs) obtained during sinus rhythm or ventricular pacing. The EGM characteristics central to identification of tissues that participate in VT circuits include low bipolar and unipolar EGM voltage and fractionated or isolated potentials. However, creation of invasive EAM significantly prolongs procedural time, and is limited by sampling density.
Late gadolinium enhancement (LGE) on cardiac magnetic resonance (CMR) can accurately characterize the transmural extent, location, and configuration of scar.10-11 Previous reports have shown that scar extent on LGE-CMR is significantly associated with left ventricular dysfunction, VT inducibility, and prognosis in patients with structural heart disease.12,13 Additionally, scar transmurality, defined as the ratio of post-infarct scar thickness (PI-ST) to left ventricular wall thickness (LV-WT), has been associated with EGM characteristics on EAM.14-22 However, the independent association of LV-WT and PI-ST with EGM characteristics has not been investigated, and no models exist for quantitative estimation of local EGM characteristics based on LGE-CMR. Scar maps can be directly imported into the procedure; however, the extent of scar transmurality and surviving muscle fibers (i.e. heterogeneity of tissues) are difficult to display. Accurate methods for extraction of critical image features are mandatory for acceptance of magnetic resonance guided catheter ablation. There thus remains a need for improved non-invasive methods and systems of producing cardiac electrogram characteristic maps for use in catheter ablation of ventricular tachycardia.